Silicon Alloy Steel

ABSTRACT

Pure silicon is a brittle insulator and, with addition of doping elements, performs as a semiconductor. It has found widespread use in computer integrated circuits as well as other semiconducting devices used in communication, electrical switching and power control. Silicon has also been used in solar collectors as active photovoltaic devices. The present application discloses formation and use of certain silicon alloys that take advantage of silicon&#39;s relatively low density near 2.33 grams per cubic centimeter and high melting temperature of 1,410° C. Alloys prepared with two to six percent boron, beryllium or mixtures thereof are strong and tough. Silicon steel containing near 2 percent alloying boron is hard while silicon alloys containing near 6 percent boron are tough and more flexible.

REFERENCES CITED

U.S. Patent Documents

Pat. No. Issue Date Author Comments 7,321,140 Jan. 22, 2008 Y Li, J JChen, Magnetron sputtered metallization of a nickel silicon alloy, LYang especially useful as solder bump barrier where the alloy containsat least 2 wt % silicon and preferably less than 20 wt %. Commerciallyavailable NiSi.sub.4.5% sputter targets have provided a superiorunder-bump metallization. 6,923,935 Aug. 2, 2005 R J Donahue, Ahypoeutectic aluminum silicon casting alloy includes T M Cleary, 10 to11.5% by weight silicon, 0.10 to 0.70% by weight K R Anderson magnesiumand also contains 0.05 to 0.07% by weight strontium. 6,149,862 Nov. 21,2000 N I Gliklad, Iron-silicon alloy product, exhibiting improvedresistance A B Kuslitskiy, to hydrogen embrittlement and method ofmaking the L A Kuslitskiy same. It has 1.38% to 1.63% weight Si, 0.10%to 0.25% weight C and 0.10% weight of at least one element from Be, Mg,Al, Ca, Sc, Ti, V, Cr, Mm, Co, Ni, Cu, Zn, W, Mo, Ge, Se, Rb, Zr, Nb,Ru, Ag, Cd, La, Ce, Pr, Nd, Gd, Tb, Dy, Er, Re, Os, Pb, Bi, U, N andother REM. 5,080,862 Jan. 14, 1992 K L Luthra Iridium silicon alloyhaving a very high resistance to oxidation contains 30 to 75 atompercent silicon. 5,049,357 Sep. 17, 1991 H Matsuno, T Takaoka, Methodfor manufacturing iron-boron-silicon alloy. Y Kikuchi, Y Kawai, T Nishi

BACKGROUND Field of Invention

Common construction steel like A36 carbon steel is more than 95 percentiron, the other constituents being <2.1% carbon, <1.65% manganese, <0.4%copper and <0.6% silicon. These carbon steels have a density of 7.8g/cm³, a yield strength of 36,000 psi (250 MPa) and an ultimate tensilestrength of 58,000-80,000 psi (400-550 MPa). A500 cold-formed steel isproduced by reducing the carbon content to 0.26% and maintainingminimums for phosphorous and sulfur. Iron melts at 1,538° C. and lowcarbon steel alloys generally corrode readily. A number of other dense,strong steel and stainless steel alloys have been produced for industry,all based on iron. Construction aluminum, like alloy 6061, is more than96 percent aluminum, the other constituents being 0.6% silicon, 0.5%iron, 0.25% copper, 0.1% manganese, 0.2% chromium, 0.15% zinc, 0.1%titanium and other elements <0.15% total. These aluminum alloys have adensity of 2.7 g/cm³, a yield strength of 8,000 psi (55 MPa), elongates25 to 30% and has an ultimate tensile strength of 18,000 psi (125 MPa).Aluminum alloys suffer from brittle fracture and aluminum melts at 660°C. producing reduced strength at elevated temperature.

Silicon is a common element, a brittle non-metallic material thus fewalloys are in wide spread use. Its advantages are a low density near2.33 g/cm³, a high melting temperature of 1,410° C. and it is not easilycorroded. The present application discloses formation of certain siliconalloys prepared with 2 to 6 percent boron or beryllium creatingmaterials that are tough, strong and not brittle as is elementalsilicon.

Description of Prior Art

Energy demands of the transportation and construction industries favorlow cost, strong, light weight materials that do not degrade over time.Silicon alloys, as disclosed in this application, are needed to fillthese requirements. A number of specialty materials have been describedthat employ silicon. U.S. Pat. No. 7,321,140, issued Jan. 22, 2008,disclose use of nickel silicon alloy for use in interconnect solderbumps. Magnetron sputtered metallization of a nickel silicon alloy wasespecially useful as solder bump barrier where the alloy contains atleast 2% silicon and preferably less than 20%. Commercially availableNiSi_(4.5) sputter targets have provided a superior under-bumpmetallization. U.S. Pat. No. 6,923,935, issued Aug. 2, 2005, describe ahypoeutectic aluminum silicon casting alloy that includes 10 to 11.5% byweight silicon, 0.10 to 0.70% by weight magnesium and also contains 0.05to 0.07% by weight strontium. A specialty iron-silicon alloy productexhibiting improved resistance to hydrogen embrittlement is described inU.S. Pat. No. 6,149,862, issued Nov. 21, 2000. It has 1.38% to 1.63%weight silicon, 0.10% to 0.25% weight carbon and 0.10% weight of atleast one element from the list Be, Mg, Al, Ca, Sc, Ti, V, Cr, Mm, Co,Ni, Cu, Zn, W, Mo, Ge, Se, Rb, Zr, Nb, Ru, Ag, Cd, La, Ce, Pr, Nd, Gd,Tb, Dy, Er, Re, Os, Pb, Bi, U or N. U.S. Pat. No. 5,080,862, issued Jan.14, 1992, teaches use of an exotic iridium silicon alloy having a veryhigh resistance to oxidation contains 30 to 75 atom percent silicon.U.S. Pat. No. 5,049,357, issued Sep. 17, 1991, describes a method foreconomically manufacturing an iron-boron-silicon alloy through simplesteps, which comprises the steps of: adding a boron raw material and acarbonaceous reducing agent to a molten iron received in a vessel;blowing oxygen gas into the molten iron to reduce the boron raw materialin the molten iron by means of the carbonaceous reducing agent toprepare a boron-containing molten iron; continuing the blowing of oxygengas to decarburize the boron-containing molten iron until the carboncontent in the boron-containing molten iron decreases to 0.2 wt. %; andadding at least one of silicon and ferrosilicon to the boron-containingmolten iron while stirring the boron-containing molten iron, therebymanufacturing an iron-boron-silicon alloy.

None of this prior art describes production or use of silicon alloyscomprising a majority of silicon with 2 to 6 percent boron or berylliumadded to produce structural alloys.

SUMMARY OF THE INVENTION

The present application discloses formation of certain silicon alloysthat are quite different from aluminum and iron based steel alloys, takeadvantage of silicon's relatively low density and high meltingtemperature of 1,410° C. These alloys as prepared with 2 to 6 percentboron or beryllium are tough, strong and resist corrosion.

It is an object of this invention, therefore, to disclose boron andberyllium silicon alloys that are tough and strong with a reducedtendency toward corrosion. Other objects of this invention will beapparent from the detailed description thereof which follows, and fromthe claims.

DETAILED DESCRIPTION OF THE INVENTION

Pure silicon is brittle and not suitable for use as a constructionmaterial. Addition of additives comprising boron and beryllium, in aconcentration range comprising 2 to 6 percent, to pure silicon formalloys with surprisingly good mechanical characteristics. These alloysare light weight in that they have densities of less than 2.7 grams percubic centimeter. Once produced, they can be cut and formed like rigidsteel.

Boron silicon alloys can be prepared by a number of methods, thesimplest being from finely divided pure elements melted under an inertatmosphere. Blending a selected concentration comprising 2 to 6 percentfinely divided elemental boron with a majority of finely dividedelemental silicon, loading into a clean alumina crucible, moving into afurnace, carefully degassing and purging with an inert atmosphere duringthe entire heating process produces the desired alloy upon cooling. Forexample, a silicon steel alloy is formed by heating a uniform mixturecontaining 4.5 percent of finely divided 99% pure elemental boron and95.5 percent of finely divided 99.5% pure elemental silicon, containedin a suitable crucible in an inert atmosphere, at 1,470° C. untilcompletely molten. Upon cooling a strong, malleable steel alloy isevident.

Beryllium silicon alloys can be prepared by blending a selectedconcentration comprising 2 to 6 percent finely divided elementalberyllium with a majority of finely divided elemental silicon, loadinginto a clean alumina crucible, moving into a furnace, carefullydegassing and purging with an inert gas atmosphere during the entireheating process produces the desired alloy upon cooling. For example, auniform mixture containing 4.5 percent of finely divided 99% pureelemental beryllium and 95.5 percent of finely divided 99.5% pureelemental silicon, contained in a suitable crucible, is heated in aninert atmosphere at 1,350° C. until completely molten. Upon cooling astrong, malleable steel alloy is formed.

EXAMPLES OF CHEMICAL CONVERSION

Specific examples of boron or beryllium silicon alloy compositions aredisclosed.

Example A: Boron Silicon Alloy Steel

A uniform mixture containing 1.125 grams of finely divided 99% pureelemental boron and 23.875 grams of finely divided 99.5% pure elementalsilicon, contained in a suitable crucible, was heated in an inertatmosphere at 1,470° C. until completely molten. Upon cooling asilver-gray colored steel alloy was found to be strong and malleable butnot brittle. Its density was 2.69 grams/cubic centimeter.

Example B: Beryllium Silicon Alloy Steel

A uniform mixture containing 1.075 grams of finely divided 99% pureelemental beryllium and 23.925 grams of finely divided 99.5% pureelemental silicon, contained in a suitable crucible, was heated in aninert atmosphere at 1,350° C. until completely molten. Upon cooling thesteel alloy was found to be strong and malleable but not brittle.

What is claimed:
 1. A process for formation of silicon steel alloycomprising melting together silicon with selected 2 to 6 percent boronin the temperature range comprising 1,400° C. to 1,800° C. in a suitablecrucible in an inert atmosphere.
 2. A process for formation of siliconsteel alloy comprising melting together silicon with selected 2 to 6percent beryllium in the temperature range comprising 1,200° C. to1,600° C. in a suitable crucible in an inert atmosphere.
 3. A processfor formation of silicon steel alloy comprising melting together siliconwith selected 2 to 6 percent boron, up to 2 percent of manganese fortoughness and up to 0.5 percent sulfur for corrosion resistance in thetemperature range comprising 1,400° C. to 1,800° C. in a suitablecrucible in an inert atmosphere.